Method and apparatus for producing thermoplastic synthetic resin sheet or film

ABSTRACT

An apparatus for producing a thermoplastic synthetic resin sheet or film has a casting mechanism having support rollers each mounted to undergo rotation about a corresponding rotational axis and one of which is mounted to undergo non-rotational displacement relative to the other support rollers. A casting sleeve is entrained around the support rollers for rotation therewith. A casting roller is mounted for undergoing rotation relative to the casting sleeve. A synthetic resin material is fed between opposite and confronting outer peripheral surfaces of the casting sleeve and the casting roller while rotating the casting sleeve and the casting roller and while effecting non-rotational displacement of one of the support rollers to holdingly press the synthetic resin material between the casting sleeve and the casting roller and thereby form the synthetic resin material into a thermoplastic synthetic resin sheet or film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national state application of copendingInternational Application Ser. No. PCT/JP03/15320, filed Dec. 1, 2003claiming a priority date of Dec. 12, 2002, and published in anon-English language.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a method for producing a thermoplasticsynthetic resin sheet or film, by which a thin sheet of a thermoplasticsynthetic resin is continuously formed and the surface thereof is madesmooth and mirror finished. The present invention also relates to anapparatus for producing the thermoplastic resin sheet or film.

2. Background Art

An example of a known apparatus for producing a thermoplastic resin isdisclosed in JP-A-6-170919. This publication describes a method forproducing a thermoplastic synthetic resin sheet or film, wherein at thedownstream side of an extrusion nozzle of a T-die, a cast drum and afirst metal roll located at the upstream side of the cast drum areprovided as a set for receiving a thermoplastic synthetic resin extrudedfrom this nozzle into the gap thereof. The peripheral surface of thefirst metal roll is coated with rubber or an elastomer having anelasticity. At the downstream side of the closest point of the cast drumand the first metal roll, a second metal roll facing the peripheralsurface of the cast drum is provided. Between these two metal rolls anda third metal roll, a metal endless belt is entrained with a constanttension. With the coated metal roll, the metal endless belt is pressedagainst the cast drum. In a section between the first and second metalrolls, the metal endless belt runs along the peripheral surface of thecast drum. Between these two metal rolls, a film-like thermoplasticsynthetic resin extruded in a molten state from the T-die is nipped andpressed in an arcuate form with use of the cast drum and the metalendless belt having corrosion resistance, and cooled and formed into asheet-like shape. Further, as an apparatus for practicing thisproduction method, this publication describes an apparatus for producinga thermoplastic synthetic resin sheet or film, wherein at the downstreamside of an extrusion nozzle of a T-die, a cast drum and a first metalroll located at the upstream side of the cast drum, are provided as aset for receiving a thermoplastic synthetic resin material extruded fromthis nozzle into the gap thereof. The first metal roll is provided sothat it moves close to or away from the cast drum. At the downstreamside of the closest point of the cast drum and the first metal roll, asecond metal roll facing the peripheral surface of the cast drum isprovided. Between these two metal rolls and a third metal roll, a metalendless belt is entrained with a constant tension. In a section betweenthe first and second metal rolls, the metal endless belt has aflexibility so that it runs along the peripheral surface of the castdrum. The the surface of the first metal roll for nipping and pressingthe metal endless belt against the cast drum is coated with aheat-resistant rubber or an elastomer having an elasticity.

Further, JP-A-7-40370 describes an apparatus for producing a syntheticresin sheet, in which a synthetic resin material continuously suppliedand fed from a die is cool-pressed with a casting mechanism having acasting roller to cast a synthetic resin sheet in a predeterminedthickness. The casting mechanism of this production apparatus comprisesa casting roller rotatably supported on a casting base block; a castingbelt means for casting a molten synthetic resin material supplied fromthe die into a predetermined thickness which circulates in contact withthe outer peripheral surface of the casting roller and moves incooperation with the casting roller; and a pressing allowance-adjustingmeans for adjusting the pressing force of the surface of the castingbelt means against the outer peripheral surface of the casting roller;wherein the casting belt means is constituted by a casting beltentrained around and between a pair of belt rollers supported by a slideframe while adjusting the distances in the upward, downward, frontwardand rearward directions, and the casting belt is located so that itfaces the outer peripheral surface of the casting roller along theoutline of the outer peripheral surface of the casting roller, whereby amolten synthetic resin material fed is pressed to form a thin sheet-likeproduct made of the synthetic resin.

By using the apparatus indicated in the above-mentioned JP-A-6-170919,it becomes possible to produce a glossy thermoplastic synthetic resinsheet or film. However, the spans between the third metal roll and thetwo metal rolls are long, the metal endless belt entrained between themetal rolls with a constant tension is too long, and spots are formed onthe produced thermoplastic synthetic resin sheet or film due to weldedjoints of the metal endless belt and scars generated by corrosionpartially on the metal endless belt, whereby it will be required toreplace the metallic belt with new one. For such purpose, however, a fewpersons (usually from 4 to 6 persons) and substantial time are requiredto detach the long metal endless belt from the metal roll having a largediameter for replacement, whereby the cost of this production apparatusis increased. In addition, since this apparatus is large in size, asmall-size apparatus with low cost is demanded at the present stage.Further, since the metal endless belt is formed by jointing metallicextended thin plates by welding into an endless belt-like form, it isrequired to process the belt smoothly so that unevenness at the jointwill not influence the sheet.

Further, even if the smooth processing is applied, since the weldingmaterial and the material of the belt are heterogeneous materials,corrosion is likely to occur at the joint of the metal endless belt, andsince the welded portion is slightly different from other portions inthe rigidity and thermal strain, its smoothness tends to be differentfrom other portions.

The apparatus disclosed in JP-A-7-40370 does not invite such a trouble,and does not cause inclusion of air at the time of casting, and makes itpossible to produce a sheet-like product or the like, of which thesurface is uniform to some extent and has a highly mirror-finishedproperty and which has a smooth or appropriately patterned surface.However, only by moving a pair of the belt rollers close to or away fromthe casting roller by forward or rearward movement of the slide frame,the casting belt is not necessarily located to an appropriate positionto face the casting roller, and in addition, it is not easy toaccurately and finely adjust the pressing force of respective beltrollers independent of the positional adjustment of the belt rollers.

Further, the synthetic resin material is, by its nature, classified intoa synthetic resin material such as acryl which tends to firmly adhere tothe casting drum or the casting roller, and a synthetic resin materialsuch as polypropylene which is relatively easily peeled off. However,with conventional apparatuses, the length for nipping and pressing themolten synthetic resin material with the casting belt and the castingroller is substantially constant, and thus, although it depends on theresin material, the time for nipping and pressing is so long that thesheet or film is hardly peeled off from the roller, whereby workabilitywill not be improved, or the time for contacting the roller becomesshort, by which adequate gloss can not be obtained.

Under such circumstances, an object of the present invention is toprovide a method for producing a thermoplastic synthetic resin sheet orfilm, and an apparatus for it, by which the production apparatus can bemade small in size and easy in handling, and a sheet or film excellentin gloss and smoothness can be obtained.

Another object of the present invention is to provide a method forproducing a thermoplastic synthetic resin sheet or film, and anapparatus therefor, in which even if the type of the synthetic resinmaterial is changed, the sheet or film can be easily peeled off from thecasting drum or the casting roller, and at the same time, adequate glosscan be obtained.

DISCLOSURE OF INVENTION

The present invention provides a method for producing a thermoplasticsynthetic resin sheet or film by cold-rolling a synthetic resin materialcontinuously supplied and fed from a die to produce a thermoplasticsynthetic resin sheet or film of a predetermined thickness, whichcomprises:

supplying and feeding a synthetic resin material between an outerperipheral surface of a rotating metallic casting roller of which theouter peripheral surface is mirror finished; and a flexible tubularmetallic seamless casting sleeve of which the outer surface is mirrorfinished and which is entrained around support rollers facing the outerperipheral surface of the casting roller and a support roller locatedaway from the casting roller so that the casting sleeve circulates incontact with in an arcuate form along a part of the outer peripheralsurface of the casting roller;

continuously casting a thermoplastic synthetic resin sheet or film bynipping and pressing by the casting roller and the casting sleeve; and

preliminarily adjusting the distance for nipping and pressing the sheetor film by the casting roller and the casting sleeve in accordance withthe peeling resistance of the synthetic resin material, in acircumferential direction along the outer peripheral surface of thecasting roller. By using this method, it is possible to cast athermoplastic synthetic resin sheet or film by the pressing forcebetween the casting roller and the flexible tubular metallic seamlesscasting sleeve of which the outer surface is mirror finished.Accordingly, a thermoplastic synthetic resin sheet or film having amirror finished or nearly mirror finished surface can be formed only byadjustment of the pressing force without inclusion of air at the time ofcasting; the thickness after casting, the surface smoothness and thespecular gloss are substantially uniform, and gloss is high; and athermoplastic synthetic resin sheet or film can be produced stably andcontinuously. Further, in the present invention, the synthetic resinmaterial means a softened synthetic resin material in a thermoplasticstate, and the die means an extrusion casting die, especially a T-die.

Further, the distance for nipping and pressing the sheet or film isadjustable along the outer peripheral surface of the casting roller inthe circumferential direction. Accordingly, even if the type of the filmor sheet is changed, the nipping and pressing distance can be adjusteddepending upon the type, whereby it is possible to prevent thethermoplastic synthetic resin sheet or film from being firmly adheredand hardly peeled.

In a case of, for example, acryl, where the peeling resistance from theouter peripheral surface of the casting roller and the surface of thecasting roller are large, it is possible to adjust the distance fornipping and pressing the sheet or film to be short by use of the castingroller and the casting sleeve, prevent the thermoplastic synthetic resinsheet or film from being firmly adhered to and hardly peeled from theouter peripheral surface of the casting roller and the surface of thecasting roller, and draw the cast glossy thermoplastic synthetic resinsheet or film from the outer peripheral surface of the casting roller.

Further, unlike the above case, in a case of, for example, polypropylenewhere the peeling resistance from the outer peripheral surface of thecasting roller and the surface of the casting sleeve are small, thedistance for nipping and pressing the sheet or film by use of thecasting roller and the casting sleeve can be increased so as to secure asufficient time for imparting the gloss and improve the productivity,whereby the thermoplastic synthetic resin sheet or film will not befirmly adhered to the outer peripheral surface of the casting roller andthe surface of the casting sleeve, and the cast glossy thermoplasticsynthetic resin sheet or film can be drawn from the outer peripheralsurface of the casting roller.

Namely, it is possible to always appropriately draw the cast glossythermoplastic synthetic resin sheet or film from the outer peripheralsurface of the casting roller, without fusing.

Further, in an embodiment of the present invention, the adjustment ofthe distance for nipping and pressing the sheet or film with the castingsleeve is carried out by rotating the second support roller facing thecasting roller at the downstream side, around the first support rollerfacing the casting roller near the die in such a direction that thesecond support roller moves close to or away from the casting roller.Accordingly, by rotating the second support roller around the firstsupport roller, the distance for nipping and pressing the sheet or filmcan be easily adjusted during the processing.

Further, in an embodiment of the present invention, the thermoplasticsynthetic resin sheet or film continuously cast by the nipping andpressing between the casting roller and the casting sleeve isimmediately introduced into a cooling tank to cool it, and aftercompletely cooling and solidifying it, a cooling liquid adhered on thesurface of the sheet is removed, and then the sheet or film is subjectedto a reheating treatment within a range of from −40° C. to +15° C. of aheat deformation temperature of the sheet or film to a degree such thata thermal strain of the sheet or film can be corrected. By thisembodiment, the thermoplastic synthetic resin sheet or film is cooled atonce, whereby its transparency can be improved and a product having nodistortion can be obtained.

Further, in an embodiment of the present invention, the pressing forceof the surface of the casting sleeve against the outer peripheralsurface of the casting roller is adjusted by moving the third supportroller which is not facing the casting roller among the support rollers.By this embodiment, even if the distance for nipping and pressing ischanged, the pressing force can be independently and simply adjusted,and the above effects can be significantly achieved, by which thethickness of the cast thermoplastic synthetic resin sheet or film caneasily be corrected or changed.

In an embodiment of the present invention, the outer peripheral surfaceof the first support roller facing the outer peripheral surface of thecasting roller near the die is covered by an elastic layer. Accordingly,fluctuation of the thickness of the synthetic resin material canappropriately be absorbed by deformation of the elastic layer.

The present invention also provides an apparatus for producing a glossythermoplastic synthetic resin sheet or film of a predetermined thicknessfrom a synthetic resin material continuously supplied and fed from a dieby use of a casting mechanism provided with a metallic casting roller,characterized in that the casting mechanism comprises: a casting rollerrotatably supported by a frame; a metallic flexible casting sleeve whichcirculates in contact with in an arcuate form along a part of the outerperipheral surface of the casting roller, and nips and presses the sheetor film in cooperation with the casting roller; and at least threesupport rollers which support the casting sleeve so as to makecirculation movement of the casting sleeve possible, wherein the castingsleeve is seamless and its outer peripheral surface is mirror finished;among the support rollers, a first support roller faces the castingroller near the die, a second support roller faces the casting roller atthe downstream side, and the second support roller is provided rotatablyaround the first support roller relative to the casting roller, a thirdsupport roller is located away from the casting roller, the secondsupport roller is provided movably so that it can adjust the distancefor nipping and pressing the sheet or film by the casting roller and thecasting sleeve i.e. the distance where the sheet or film underprocessing is in a close contact with the casting roller and the castingsleeve. By using this apparatus, the production method of the presentinvention can be securely practiced.

Further, in an embodiment of the present invention, the second supportroller is provided at the free end side of a support lever pivotallymounted around the same axis as the first support roller so that thesupport roller is moved by rotating the support lever by an adjustingmeans. By this embodiment, the second support roller can easily bemoved. And, by providing a feed screw mechanism between the frame andthe support lever as the adjusting means, the adjustment can furthereasily be made.

Further, in an embodiment of the present invention, the first, secondand third support rollers are located at apexes of a triangle, and thethird support roller is located on the frame so that the support rolleris movable away from the outer peripheral surface of the casting rollerso as to adjust the tension of the casting sleeve, whereby the pressingforce can easily be adjusted, the apparatus can be made totally small insize as compared with conventional apparatuses, and the casting sleevecan easily be replaced with new one.

In an embodiment of the present invention, among the support rollers,the first support roller facing the outer peripheral surface of thecasting roller near the die, is covered on its outer peripheral surfacewith an elastic layer of rubber, an elastomer or the like having thermalresistance and elasticity, whereby the fluctuation of the thickness ofthe thermoplastic synthetic resin sheet or film supplied from the diecan be absorbed.

Further, in an embodiment of the present invention, the third supportroller is provided on the frame in parallel or nonparallel to the firstand second support rollers in such a manner that the distance betweenthe axes of the rollers are changeable, whereby by moving the thirdsupport roller to the inside of the casting sleeve to loosen the tensionof the casting sleeve, the casting sleeve abraded in use can be detachedfrom these support rollers and replaced with new one, and in addition,when the casting sleeve is eccentrically arranged and the thickness ofthe thermoplastic synthetic resin sheet or film becomes irregular, oneend of the third support roller is slanted in such a direction that theeccentric arrangement can be corrected, whereby the eccentricarrangement of the casting sleeve can easily be corrected.

In an embodiment of the present invention, the diameter of the castingroller is from 1 to 3 times the diameter of the first support roller,and the diameter of the first support roller is from 1 to 1.5 times thediameter of the second support roller and the diameter of the thirdsupport roller, whereby these support rollers can be located near theouter peripheral surface of the casting roller, a thermoplasticsynthetic resin sheet or film can be produced by a predeterminedpressing force without enlarging the size of the casting sleeve, and theapparatus can be made totally small and operated with low costs.

In an embodiment of the present invention, the casting sleeve is made ofnickel and formed by a seamless process, and has a thickness of 0.2 to0.5 mm and a diameter of 400 to 1,000 mm, whereby the above-mentionedeffects can further significantly obtained.

In an embodiment of the present invention, the diameters of the supportrollers are from 600 to 1,000 times the thickness of the casting sleeve,whereby excessive deformation by bending will not be caused, and theuseful life time of the casting sleeve will be lengthened. If this valueis less than 600 times, the useful life time will become extremelyshort, and if this value exceeds 1,000 times, the apparatus will becomelarge in size, such being not advisable.

Further, in an embodiment of the present invention, at the downstreamside of the second support roller facing the casting roller,sequentially provided are a cooling tank for immersing the thermoplasticsynthetic resin sheet or film; a draining means for draining water onthe surface of the sheet or film; and a sheet-correcting and -heatingdevice (37) for a reheating treatment within a range of from −40° C. to+15° C. of a heat deformation temperature of the sheet or film to adegree such that a thermal strain of the sheet or film can be corrected,whereby, the film or sheet can be cooled further rapidly, thetransparency can further be improved, and products having no distortioncan be produced. Further, in a case of a non-crystalline synthetic resinsheet or film for which no transparency is required, for example,polycarbonate, the sheet or film can be supplied directly to a secondaryprocessing apparatus from the casting roller.

Further, in an embodiment of the present invention, the cooling tank isprovided on the frame in an elevationally adjustable fashion, thesheet-correcting and -heating device. is provided on another frame whichis connectable to the frame, and the frames are movable on aninstallation face, whereby it becomes easy to provide the die with thecasting apparatus, the cooling tank and the sheet-correcting and-heating device, and further, when the cooling tank is not necessary, itcan be retracted from the passage of the film or sheet. Further, byretracting the cooling tank, it will not interfere the preparationbefore the start of operation and the workability will be high.

With respect to polypropylene as one type of the thermoplastic syntheticresin to be used in the present invention, a crystalline propylenemonopolymer, or a crystalline copolymer obtained by copolymerizingpropylene with a comonomer other than propylene, such as ethylene orbutene, and a mixture thereof may be used. Further, to suchpolypropylene, an antioxidant, lubricant, an antistatic agent, aslipping additive, an antiblocking agent, an ultraviolet absorber, anucleating agent, a transparency-improving agent, an organic peroxide, apigment, inorganic fillers such as talc or calcium carbonate, organicfillers such as wood flour or synthetic fibers, other thermoplasticsynthetic resin such as polyethylene or ethylene propylene rubber,rubber and the like, may appropriately be added for use, as the caserequires.

Further, as other thermoplastic synthetic resin, polyethylene,polystyrene, ABS, polyethylene, terephthalate, polybutyleneterephthalate, polyamide, polycarbonate, vinyl chloride and the like maybe used. In the foregoing, explanation has been made on the case of asingle sheet, etc. However, the method for producing a sheet or film andthe apparatus therefor of the present invention may be applied toproduction of a multi-layer sheet or a laminated sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fundamental side view showing an example of the apparatuspracticing the method of the present invention.

FIG. 2 is a side view of a casting mechanism part showing a supportingstructure of the second support roller in FIG. 1.

FIG. 3 is a plan view showing the mechanism of the casting sleeve andthe support part.

FIG. 4 is a fundamental side view showing the mechanism of anotherexample including a cooling device of a post treatment step.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1

Referring to FIG. 1 and FIG. 2, an apparatus 10 of the present inventionis constructed as described below so that a synthetic resin materialcontinuously supplied and fed from an extrusion casting die 11, i.e., amolten synthetic resin material FO heated to its heat deformationtemperature, is subjected to cool-pressing with a casting mechanism 13provided with a casting roller 12 to produce a glossy thermoplasticsynthetic resin sheet or film F of a predetermined thickness.

The casting mechanism 13 comprises a casting roller 12 rotatably andhorizontally supported by a frame 14; a flexible tubular metallicseamless casting sleeve 15 of which the outer surface is mirrorfinished, which rotates in contact with in an arcuate form a part of theouter peripheral surface of the casting roller 12 and nips and pressesthe synthetic resin material FO continuously supplied from the extrusioncasting die 11 together with the casting roller 12; and a first supportroller 16 and a second support roller 17 which face the outer peripheralsurface of the casting roller 12 and are capable of adjusting thepressing force between the casting roller 12 and the surface of thecasting sleeve 15. The casting roller 12 is also provided on the frame14 so that it is movable close to or away from the support rollers 16,17 (see FIG. 3).

Further, as the casting sleeve 15, one manufactured by Dimuco Co. wasused, and as is defined in Claim 1 of JP-A-2001-330081, this is producedby subjecting a metallic cylindrical simple tube for which thermoplasticprocessing is applicable to a thin-wall treatment to reduce thethickness to a predetermined level, and then cutting the thin-walledcylindrical simple tube to a desired width to form a ring-like product.

The casting sleeve 15 has a structure wherein three metallic supportrollers 16, 17, 18 each having a horizontal axial line, including athird support roller 18 located away from the casting roller 12, arelocated at apexes of a triangle and the casting sleeve 15 is entrainedaround the respective rollers in a triangle form, and the casting sleeve15 faces the outer peripheral surface of the casting roller 12 in anarcuate form at a portion along the outline of the outer peripheralsurface of the casting roller 12. Further, the support rollers may beconstituted by 4 or more rollers.

The frame 14 is designed to have wheels and be movable on aninstallation face (including rails), and be fixed at the position atwhich centering of the casting mechanism 13 and the die 11 is made.

The tension of the casting sleeve 15 can be adjusted by adjusting thedistances among the support rollers 16, 17, 18.

Among the support rollers 16, 17, 18, the first support roller 16 nearthe die 11 is on its outer peripheral surface covered with an elasticlayer 19 made of rubber or elastomer having heat resistance andelasticity; provided on the frame 14 so that it faces the outerperipheral surface of the casting roller 12 and is rotatable around thehorizontal axial line thereof; and as indicated in FIG. 3, bearings 20a, 20 b are provided so that these are finely adjustable to move closeto or away from the casting roller 12.

The distance for nipping and pressing the sheet or film, that is, adistance S where the sheet or film under processing is in closelycontact with the casting roller 12 and the casting sleeve 15, isdesigned to be adjustable in a circumferential direction along the outerperipheral surface of the casting roller 12. In this example, the secondsupport roller 17 located at a distance in the downstream side from thefirst support roller 16, is provided in a direction to move close to oraway from the outer peripheral surface of the casting roller 12 aroundthe first support roller 16.

Specifically, as indicated in FIG. 2, the second support roller 17 isprovided so that it will be movable in a direction to move close to oraway from the outer peripheral surface of the casting roller 12, via anadjusting means, for example, a feed screw mechanism including anelectric motor M, usually a ball screw mechanism B, wherein a bearing ofthe second support roller 17 is supported at the free end side of asupport lever 26, of which the basal portion is pivotally mounted aroundthe same axis as the axis of the first support roller 16, so that thesupport lever 26 is rotated around the horizontal axial line of thepivotally mounted basal portion. As the adjusting means, in addition tothe electric motor M and the feed screw B, a pneumatic or hydrauliccylinder actuator, a rotation mechanism of the support lever 26 by useof a degree of insertion of cotter, and the like, maybe used. Otherwise,even by a manual operation, no substantial change is brought about inthe present invention.

The third support roller 18 is provided on the frame 14 so that itsposition is changeable, for correction of the eccentric arrangement anddeformation of the casting sleeve 15.

Within the casting sleeve 15, the third support roller 18 is arranged inparallel or nonparallel to the other support rollers 16, 17 whilekeeping its axial line horizontally, and the distances between axes fromthese rollers can be changed or fixed. Although its mechanism is notparticularly restricted, for example, the bearings at both sides of thethird support roller 18 are all together supported by a support block 21pivotally mounted on the frame 14 so that it can be widely moved closeto or away from the other support rollers, and finely adjustable inparallel or nonparallel to the other support rollers 16, 17 for eachside of the support block 21 corresponding to the left or right bearing22. Further, the third support roller 18 takes a part of a tensionroller for adjusting the tension of the casting sleeve.

The diameter of the casting roller 12 is about 1 to 3 times the diameterof the first support roller 16, and in the example indicated in thefigure, it is about 1.6 times. The diameter of the first support roller16 is 1 to 1.5 times the diameter of the second support roller 17 andthe diameter of the third support roller 18, and in the exampleindicated in the figure, it is about 1.25 times. However, the presentinvention is not particularly restricted to this diameter ratio.

The casting sleeve 15 is made of nickel and formed by a seamlessprocess, and has a thickness of about 0.2 to 0.5 mm and a diameter ofabout 400 to 1,000 mm, and in the example, the thickness is about 0.3 mmand the diameter is about 500 mm.

With respect to the above dimension, the one having the diameters of thesupport rollers 16, 17 and 18 of 250, 200 and 200 mm, respectively, issufficient for practical use, and when the thickness is 0.3 mm, thecasting sleeve 15 is deformed adequately and undergoes elasticdeformation without overloading the peripheral surfaces of the supportrollers 16, 17 and 18, and can adequately endure the repeated bendingstress.

As the material for the casting sleeve, instead of the one made ofnickel, other nickel alloy, stainless steel, titanium alloy or the likemay be used. Further, the thicknesses of the casting sleeve 15 and thefilm or sheet under processing in FIG. 2 are illustrated exaggeratinglyfor convenience in explanation.

In the casting mechanism 13, although omitted in the figure, atemperature-adjusting mechanism for heating or cooling the syntheticresin material FO is provided at an appropriate position, by which thetemperature of the casting roller 12 and the circulated casting sleeve15 is adjusted, whereby the temperature control of the synthetic resinmaterial FO becomes possible. The temperature adjustment of the castingsleeve 15 may be made by providing a temperature-adjusting mechanism forheating or cooling in the support rollers 16, 17, 18. Further, in thecasting sleeve 15, an apparatus for blowing a temperature-controlled airmay be additionally provided.

In production of the sheet or film by use of the above apparatus, priorto the casting, the frame 14 is moved on the installation face,centering of the casting mechanism 13 and the resin-ejecting port of thedie 11 is conducted, and at the centering position, the frame 14 isfixed to the installation face with an appropriate fixing means.

The outer peripheral surface of the casting roller 12 and the castingsleeve 15 entrained in a triangle form around the support rollers 16,17, 18, are brought into contact to each other at a section between thefirst support roller 16 and the second support roller 17, the firstsupport roller 16 and the second support roller 17 are moved close tothe casting roller 12, the positions thereof are finely adjusteddepending upon the thickness, material and the like of the film orsheet, and the third support roller 18 is moved away from the first andsecond support rollers 16, 17 to impart a desired tension to the castingsleeve 15. Then, the synthetic resin material FO is supplied and fedfrom the die 11 into the gap between the casting roller 12 and thecasting sleeve 15 circulating and moving in contact with the castingroller 12, and by the nipping and pressing by use of the casting roller12 and the casting sleeve 15, a thermoplastic synthetic resin sheet orfilm F is continuously cast.

Further, by the elastic layer 19 and the deformation of the castingsleeve 15 at the section between the first support roller 16 and thesecond support roller 17, the pressing force can be adjusted, and evenif an irregular thickness portion or a partly irregular thicknessportion exists within this section, the synthetic resin material FOextruded from the extrusion casting die 11 is fed into the gap betweenthe casting roller 12 and the casting sleeve 15 by the deformation ofthe elastic layer 19, whereby the material is pressed into a uniformthickness.

In a case where the type of the synthetic resin material constitutingthe film or sheet F is changed to, for example, acryl which presents alarge peeling resistance from the outer peripheral surface of thecasting roller 12 and the surface of the casting sleeve 15, the secondsupport roller 17 is moved away from the outer peripheral surface of thecasting roller 12 by rotating the support lever 26 by use of theadjusting means, by which the nipping and pressing distance of thethermoplastic synthetic resin sheet or film by the outer peripheralsurface of the casting roller 12 and the surface of the casting sleeve15 i.e. the distance S where the sheet or film under processing is inclosely contact with the casting roller 12 and the casting sleeve 15(see FIG. 2) is adjusted to be short, whereby it is possible to preventthe thermoplastic synthetic resin sheet or film from being firmlyadhered to and hardly peeled from the outer peripheral surface of thecasting roller 12 and the surface of the casting sleeve 15, and draw thecast thermoplastic synthetic resin sheet or film from the outerperipheral surface of the casting roller 12.

Further, on the contrary, in a case of, for example, polypropylene,where the peeling resistance from the outer peripheral surface of thecasting roller 12 and the surface of the casting sleeve 15 is small, thesecond support roller 17 is moved close to the outer peripheral surfaceof the casting roller 12, by which the nipping and pressing distance Sof the thermoplastic synthetic resin sheet or film by the outerperipheral surface of the casting roller 12 and the surface of thecasting sleeve 15 is adjusted to be long, whereby sufficient time forimparting gloss is ensured and the productivity is improved.

In a case where the thickness of the sheet or film F is changed, if thewidth is kept the same, it is advisable to change the extrusion amountper unit time, and therefore, the distance at a part of nipping andpressing by the casting roller 12 and the casting sleeve 15 is changed,and correspondingly, the positions of the first and second supportrollers 16 and 17 against the casting roller 12 are finely adjusted forchange of the extrusion amount per unit time.

Namely, when a thin sheet or film F is cast, these support rollers 16,17 are moved close to the casting roller 12 to narrow the gap betweenthe casting roller 12 and the casting sleeve 15, and when a thick sheetor film F is cast, the extrusion amount per unit time from the die 11 isincreased, and the first and second support rollers 16 and 17 are movedaway from the casting roller 12 correspondingly.

Since the support roller 16 has an elastic layer 19 on its surface, itwill receive a resistance from the synthetic resin material FO underprocessing during the casting, and this elastic layer 19 undergoeselastic deformation, and a gap for absorbing the fluctuation of thethickness of the synthetic resin material is formed between the castingroller 12 and the casting sleeve 15. When no load is applied beforeprocessing, it is advisable to prevent the casting roller 12 fromcontacting the casting sleeve 15 to prevent formation of scars or thecasting roller 12.

The movement of the support rollers 16, 17 and 18 and the bearings 20,22 is preferably made by fine adjustment with an electric motor of whichthe feed screws 23, 24 are connected to them via a reduction gearmechanism. However, the adjustment may be made by a pneumatic orhydraulic cylinder actuator, a degree of insertion of cotter, and thelike, and the gap between the casting sleeve 15 and the casting roller12 can likewise be adjusted. Further, the feed screws 23, 24 and cottermay be actuated by the above actuating means. In addition, even by amanual operation, no substantial change is brought about in the presentinvention.

Further, in a case where the casting sleeve 15 eccentrically exists toone side on the three support rollers 16, 17, 18 during casting, it isadvisable to adjust the degree of parallelization of the axial line ofthe third support roller 18 and the axial lines of other support rollers16, 17, to correct the eccentric arrangement of the casting sleeve 15.

Namely, the tendency that the casting sleeve 15 shifts towards the lowresistance side is unavoidably caused by slight temperature differencebetween left and right sides of the synthetic resin material FO layer tobe supplied, slight difference in the degree of parallelization ofsupport rollers 16, 17, 18, the difference in the resistance to plasticdeformation and the like. Accordingly, in usual, correction is made by,for example, bringing the side edge of the casting sleeve 15 intocontact with a guide, but by such a method, the casting sleeve isdamaged.

In the present invention, by slightly changing the degree ofparallelization of the axial line of the third support roller 18relative to the other support rollers 16, 17, an effect of, for example,a type of a turn bar is generated, the position of the casting sleeve 15can be easily returned correctly to the center of the support rollers16, 17 and 18. When the position of the casting sleeve 15 is returned tothe center position, the third support roller 18 may be returned to theangle at which the casting sleeve 15 will maintain the center positionof the three support rollers 16, 17 and 18.

The casting sleeve 15 can always be kept at the correct position bydetecting the position of the side edge of the casting sleeve 15 with aline regulator, and corresponding to this detected value, changing theaxial direction of the third support roller 18.

In order to exhibit the effect like the turn bar, a block guide 25 ofthe third support roller 18 is provided so that it may be moved oradjusted to upper and lower directions (see white arrow) with the leftand right sides being adjustable independently, and may be fixed, inFIG. 2.

Further, in a case where the thicknesses of the left and right sides ofthe cast film F are different, the distance where the left and rightbearings 20 a, 20 b of the first and second support rollers 16 and 17are close to the casting roller 12 may be finely adjusted forcorrection.

Then, in a case where the casting sleeve 15 is abraded in use andreplaced with new one, the third support roller 18 is moved largely tothe inside of the casting sleeve 15 to loosen the tension of the castingsleeve 15, and the casting roller 12 is moved away from the supportrollers 16, 17, and then the support rollers 16, 17 and 18 arecantilevered, and the casting sleeve 15 is detached from the supportrollers 16, 17, 18 and replaced with new one.

Further, in the explanation of this example, a case where the syntheticresin material FO is fed along the vertical direction from the die 11i.e. a vertical extrusion system is explained. However, this example canlikewise be carried out in a case where the material is fed along thehorizontal direction i.e. lateral extrusion system.

Example 2

This example is used as a post treatment of the production apparatusindicated in the above example; and as indicated in FIG. 4, a coolingtank 30 for immersing a thermoplastic resin sheet or film F is providedclose to the downstream side of the second support roller 17 facing thecasting roller 12; and at the downstream side of the cooling tank 30, adraining blower 36 as a draining means for draining water on the cooledsheet or film F. At the further downstream side of the draining blower36, is provided a sheet-correcting and -heating device 37 having aplurality of heating rollers 39 for a reheating treatment within a rangeof from −40° C. to +15° C. of a heat deformation temperature of thesheet or film F to a degree such that a thermal strain of the sheet orfilm F can be corrected. The cooling tank 30 is provided on the frame 14so that the cooling tank is movable upward and downward, thesheet-correcting and -heating device 37 is provided on another frame 27which is connectable to the frame 14, and the frames 14, 27 are movableon an installation face and fixed at a predetermined position.

In the water of the cooling tank 30, a plurality of guide rollers 31,32, 33 are provided, and the film or sheet F is entrained around therollers in a zigzag fashion and sequentially cooled.

Further, at the upper side of the cooling tank 30, guide rollers 38 areprovided to form a passage through which the film or sheet F usuallydoes not pass, and by permitting the sheet or film F to pass through theguide rollers 38, the sheet or film can be sequentially reheated forannealing treatment without cooling in water.

After nipping and pressing by the casting roller 12 and the castingsleeve 15, by directly immersing the glossy film or sheet F of which thesurface is nearly mirror finished in a cooling tank 30 for cooling, thetransparency of the film or sheet F can further be improved.

For the one for which no transparency is required, the film or sheet Fis permitted to pass through the guide rollers 38 and supplied to thesheet-correcting and -heating device 37 without passing it through thecooling tank 30, for reheating treatment of the film or sheet F.

Further, one other than a crystalline thermoplastic synthetic resin filmor sheet, may sometimes be supplied directly to a secondary processingapparatus (not shown in the figure) without passing it through thecooling tank 30 and the sheet-correcting and -heating device 37.

According to the present invention, it is possible to obtain anapparatus being small in size and easy to handle, and cast athermoplastic synthetic resin sheet or film stably and continuously.Further, even if the type of the synthetic resin material is changed,the sheet or film can be efficiently produced by preliminarily adjustingthe nipping and pressing distance i.e. the distance where the sheet orfilm under processing is in closely contact with the casting roller andthe casting sleeve, depending upon the degree of the peeling resistanceto the casting roller or casting sleeve. Accordingly, it is possible toobtain a sheet or film excellent in gloss and smoothness from varioustypes of synthetic resin materials.

1. A method for producing a thermoplastic synthetic resin sheet or film by cold-rolling a synthetic resin material continuously supplied and fed from a die to produce a thermoplastic synthetic resin sheet or film of a predetermined thickness, comprising the steps of: supplying and feeding a synthetic resin material between an outer peripheral surface of a rotating metallic casting roller and a flexible tubular metallic seamless casting sleeve entrained around first and second support rollers confronting the outer peripheral surface of the casting roller and a third support roller disposed at a greater distance from the outer peripheral surface of the casting roller than the first and second support rollers so that the casting sleeve circulates along an arcuate path while contacting a part of the outer peripheral surface of the rotating casting roller; continuously casting a thermoplastic synthetic resin sheet or film by nipping and pressing the synthetic resin material with the casting roller and the casting sleeve; and adjusting a distance for nipping and pressing the synthetic resin material by the casting roller and the casting sleeve in a circumferential direction along the outer peripheral surface of the casting roller and in accordance with a peeling resistance of the synthetic resin material; wherein the step of adjusting a distance for nipping and pressing the synthetic resin sheet or film with the casting sleeve is carried out by rotating the second support roller confronting the casting roller at the downstream side, around the first support roller confronting the casting roller near the die in such a direction that the second support roller is moved toward and away from the casting roller.
 2. The method for producing a thermoplastic synthetic resin sheet or film according to claim 1; wherein the outer peripheral surface of the first support roller facing the casting roller near the die is covered by an elastic layer, and fluctuation of the thickness of the synthetic resin material is absorbed by deformation of the elastic layer.
 3. An apparatus f or producing a thermoplastic synthetic resin sheet or film by cold-rolling a synthetic resin material continuously supplied and fed from a die to produce a glossy thermoplastic synthetic resin sheet or film of a predetermined thickness, the apparatus comprising: a casting mechanism having a frame; a metallic casting roller supported by the frame for undergoing rotation; a flexible and seamless metallic casting sleeve having a mirror-finished outer peripheral surface and being mounted for undergoing rotational movement along an arcuate path while contacting a part of an outer peripheral surface of the casting roller to nip and press a synthetic resin material supplied therebetween; and at least three support rollers for rotating the casting sleeve and comprised of first, second and third support rollers; wherein the first support roller confronts the casting roller near a die, the third support roller is disposed at a greater distance from the casting roller than the first and second support rollers, and the second support roller confronts the casting roller at the downstream side and is mounted for undergoing rotational movement around the first support roller relative to the outer peripheral surface of the casting roller to adjust a distance between the casting roller and the casting sleeve during nipping and pressing of the synthetic resin material supplied therebetween, and wherein the second support roller is provided at the free end side of a support lever pivotally mounted around the same axis as the first support roller so that the second support roller is moved by rotating the support lever by an adjusting means.
 4. The apparatus for producing a thermoplastic synthetic resin sheet or film according to claim 3; wherein the adjusting means is a feed screw mechanism provided between the frame and the support lever.
 5. The apparatus for producing a thermoplastic synthetic resin sheet or film according to. claim 3; wherein among the support rollers, the first support roller facing the outer peripheral surface of the casting roller near the die, is covered on its outer peripheral surface with an elastic resistance and elasticity.
 6. The apparatus for producing a thermoplastic synthetic resin sheet or film according to claim 3; wherein the casting sleeve is made of nickel and formed by a seamless process, and has a thickness of 0.2 to 0.5 mm and a diameter of 400 to 1,000 mm.
 7. A method for producing a thermoplastic synthetic resin sheet or film by cold-rolling a synthetic resin material continuously supplied and fed from a die to produce a thermoplastic synthetic resin sheet or film of a predetermined thickness, comprising the steps of: supplying and feeding a synthetic resin material between an outer peripheral surface of a rotating metallic casting roller and a flexible tubular metallic seamless casting sleeve entrained around first and second support rollers confronting the outer peripheral surface of the casting roller and a third support roller disposed at a greater distance from the outer peripheral surface of the casting roller than the first and second support rollers so that the casting sleeve circulates along an arcuate path while contacting a part of the outer peripheral surface of the rotating casting roller; continuously casting a thermoplastic synthetic resin sheet or film by nipping and pressing the synthetic resin material with the casting roller and the casting sleeve; and adjusting a distance for nipping and pressing the synthetic resin material by the casting roller and the casting sleeve in a circumferential direction along the outer peripheral surface of the casting roller and in accordance with a peeling resistance of the synthetic resin material; wherein the step of adjusting a distance for nipping and pressing the synthetic resin sheet or film with the casting sleeve is carried out by rotating the second support roller confronting the casting roller at the downstream side, around the first support roller confronting the casting roller near the die in such a direction that the second support roller is moved toward and away from the casting roller; and wherein the thermoplastic synthetic resin sheet or film continuously cast by the nipping and pressing between the casting roller and the casting sleeve is immediately introduced into a cooling tank to cool it, and after completely cooling and solidifying it, a cooling liquid adhered on the surface of the sheet is removed, and then the sheet or film is subjected to a reheating treatment within a range of from −40° C. to +15° C. of a heat deformation temperature of the sheet or film to a degree such that a thermal strain of the sheet or film can be corrected.
 8. An apparatus for producing a thermoplastic synthetic resin sheet or film by cold-rolling a synthetic resin material continuously supplied and fed from a die to produce a glossy thermoplastic synthetic resin sheet or film of a predetermined thickness, the apparatus comprising: a casting mechanism having a frame; a metallic casting roller supported by the frame for undergoing rotation; a flexible and seamless metallic casting sleeve having a mirror-finished outer peripheral surface and being mounted for undergoing rotational movement along an arcuate path while contacting a part of an outer peripheral surface of the casting roller to nip and press a synthetic resin material supplied therebetween; and at least three support rollers for rotating the casting sleeve and comprised of first, second and third support rollers; wherein the first support roller confronts the casting roller near a die, the third support roller is disposed at a greater distance from the casting roller than the first and second support rollers, and the second support roller confronts the casting roller at the downstream side and is mounted for undergoing rotational movement around the first support roller relative to the outer peripheral surface of the casting roller to adjust a distance between the casting roller and the casting sleeve during nipping and pressing of the synthetic resin material supplied therebetween, and wherein the second support roller is provided at the free end side of a support lever pivotally mounted around the same axis as the first support roller so that the second support roller is moved by rotating the support lever by an adjusting means, wherein at the downstream side of the second support roller facing the casting roller, sequentially provided are a cooling tank for immersing the thermoplastic synthetic resin sheet or film, draining means f or draining water on the surface of the sheet or film, and a sheet-correcting-and-heating device for a reheating treatment within a range of from −40° C. to +15° C. of a heat deformation temperature of the sheet or film to a degree such that a thermal strain of the sheet or film can be corrected.
 9. The apparatus for producing a thermoplastic synthetic resin sheet or film according to claim 8; wherein the adjusting means is a feed screw mechanism provided between the frame and the support lever.
 10. The apparatus for producing a thermoplastic synthetic resin sheet or film according to claim 8; wherein among the support rollers, the first support roller facing the outer peripheral surface of the casting roller near the die, is covered on its outer peripheral surface with an elastic resistance and elasticity.
 11. The apparatus for producing a thermoplastic synthetic resin sheet or film according to claim 10; wherein the casting sleeve is made of nickel and formed by a seamless process, and has a thickness of 0.2 to 0.5 mm and a diameter of 400 to 1,000 mm. 